1. Field of the Invention
The present invention relates to an optical pickup apparatus for respectively recording and reproducing information respectively to and from optical disks having different board thicknesses of DVD (Digital Versatile Disk), CD (Compact Disk) or the like, particularly relates to an optical pickup apparatus capable of providing excellent spot light of a beam of laser light eliminating astigmatism and comma aberration.
2. Description of the Related Art
In a background art, according to an optical pickup apparatus using two laser diodes for emitting beams of laser light having different wave length, as shown by FIG. 3, a beam A of laser light emitted from a laser diode 11 is made to transmit a dichroic prism 13 and a deflecting beam splitter 14, further, a beam B emitted from a laser diode 12 is refracted by the dichroic prism 13 to coincide with an optical axis of the beam A, refracted in a direction orthogonal to an information recording face of an optical disk 21 to constitute a parallel beam by a collimator lens 16, deflected from elliptically polarized light to linearly polarized light by a quarter-wave prism 17 and is converged into spot light of the beam of laser light to the optical disk 21 by an object lens 18, and reflected light thereof is refracted in a direction of an optical detecting element 20 by the deflecting beam splitter 14 and is detected by the optical detecting element 20 via a cylindrical lens 19. Therefore, the dichroic prism 13 and the deflecting beam splitter 14 which are expensive optical parts are needed, and there poses a problem that a number of pieces of optical parts is increased and the optical pickup apparatus becomes expensive. Further, in reference to FIG. 4, two parallel flat plate half mirrors 33, 34 are used in place of the dichroic prism 13 and the deflecting beam splitter 14 which are the expensive optical parts of FIG. 3, a beam A of laser light emitted from a laser diode 31 is refracted to transmit by the parallel flat plate half mirrors 33, 34 arranged by angles orthogonal to an optical axis (in the drawing, the parallel flat plate half mirrors 33, 34 are shown simplifiedly two-dimensionally) further, a beam of laser light emitted from a laser diode 32 is refracted by the parallel flat plate half mirror 34 to coincide with the optical axis of the beam A of laser light, refracted by a total reflection mirror 35 in a direction orthogonal to an information recording face of an optical disk 40 to constitute a parallel beam by a collimator lens 36, deflected from elliptically polarized light to linearly polarized light by a quarter-wave plate 37 and is converged to spot light of the beam of laser light to the optical disk 40 by an object lens 38, and reflected light thereof is refracted in a direction of the optical detecting element 39 by the parallel flat plate half mirror 33 and is detected by the optical detecting element 39. However, when the beam of laser light emitted from the laser diode 31 is refracted to pass by the two parallel flat plate half mirrors 33, 34, astigmatism and comma aberration are generated and there poses a problem that excellent spot of the beam of laser light cannot be converged to the information recording face of the optical disk 40.
There is a background art in which a first parallel flat plate half mirror is arranged relative to an optical axis of Z axis of a beam of laser light emitted from one laser diode of two laser diodes having different wave lengths by being inclined around Y axis by an angle q, a second parallel flat plate half mirror having a plate thickness the same as that of the first parallel flat plate half mirror is arranged by being inclined around X axis by an angle q, the beam of laser light emitted from the one laser diode is successively refracted to transmit the first and the second parallel flat plate half mirrors, and the laser beam emitted from other laser beam diode is reflected by the second parallel flat plate half mirror to coincide the optical axes of the beams of laser light emitted from the two laser diodes having the different wave lengths (refer to, for example, JP-A-2001-006205).
Further, there is a configuration in which an inclination adjusting member is brought into contact with a lens, and by conducting electricity to a solenoid coil provided at a movable support member and a magnet provided at a fixed member in a state of bringing the inclination adjusting member into contact with the lens, the movable support member is displaced and an inclination of the lens is adjusted by pressing the lens to the inclination adjusting member (refer, for example, Japanese Patent Publication No. 3392904).
Further, there is a configuration in which first laser light from a first laser diode is reflected by a parallel flat plate half mirror, a reflected beam of the first laser light is converged by a converging lens, the converged beam of first laser light is shaped by a beam shaping prism and is converged to a first optical disk in correspondence with the first laser light, laser light from a second laser diode transmitted through a parallel flat plate half mirror is provided with astigmatism, second laser light from the second laser diode is converged to a second optical disk in correspondence with the second laser light, and astigmatism generated in passing a beam of the second light through the beam shaping prism is reduced (refer to, for example, JP-A-2001-344801).
Further, beams of respective laser light emitted from laser diodes for emitting two or more of beams of laser light having different wave lengths are converged by an object lens, beams of respective laser light reflected by an optical disk and passing through an object lens are detected by an optical detecting element, positions of returning the beams of respective laser light emitted from the laser diodes on optical paths between the laser diodes and the optical detecting element are made to coincide with each other at a light receiving face of the optical detecting element, and comma aberration is corrected by a hologram optical element (refer to, for example, JP-A-2003-317302).